Recently much public attention has been drawn to the issue of youth violence, particularly that associated with drug abuse. It is well documented that anabolic steroid use in adolescent teenagers is associated with a higher incidence of aggression and violence. However, the basic biobehavioral processes underlying the development and maintenance of the aggressive phenotype following adolescent anabolic steroid exposure remain unknown. Recently, we have used peripubertal Syrian hamsters (Mesocricetus auratus) as an "adolescent" animal model to show that anabolic steroid exposure during this period facilitates the development of a highly aggressive behavioral phenotype when tested as young adults. In addition, aggressive, anabolic steroid-treated adult animals present with altered brain chemistry, specifically vasopressin and serotonin afferent innervation to the anterior hypothalamic brain region implicated in the regulation of offensive aggression. The research outlined in this proposal is a continuation of our work on adolescent anabolic steroids and the behavioral neurobiology of aggression. These studies examine the biobehavioral effects of adolescent anabolic steroid exposure on aggression permanence and the anatomy and function of the anterior hypothalamic vasopressin and serotonin neural network controlling this behavior in hamsters. It is hypothesized that adolescent anabolic steroids disrupt the signaling equilibrium between anterior hypothalamic vasopressin and serotonin, facilitating the development and maintenance of the aggressive phenotype. It is possible that this disruption occurs at the level of the signal molecules themselves, and/or at the level of their receptors. To test this, we are asking two questions: (1) how has adolescent anabolic steroid exposure affected the vasopressin and serotonin neural systems and (2) are the changes in behavior and neurobiology permanent? Completion of the proposed research should provide new insight into the basic biobehavioral processes regulating adolescent anabolic steroid-induced aggression. This knowledge could provide a scientific basis for the rational treatment of aggressive, anabolic steroid abusers and a better understanding of the behavioral and biological changes that may predispose young individuals to behave in a self-destructive or violent manner later in Iife.